Teach TreeTransform and family how to transform generic lambdas within templates and nested within themselves.

  
This does not yet include capturing (that is next).

Please see test file for examples.

This patch was LGTM'd by Doug:
http://llvm-reviews.chandlerc.com/D1784
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130930/090048.html

When I first committed this patch - a bunch of buildbots were unable to compile the code that VS2010 seemed to compile.  Seems like there was a dependency on Sema/Template.h which VS did not seem to need, but I have now added for the other compilers.  It still compiles on Visual Studio 2010 - lets hope the buildbots remain quiet (please!)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191879 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 153 insertions, 28 deletions

diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 32111bac3a..29481d6c63 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -14,6 +14,7 @@
 #include "TreeTransform.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTLambda.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
 #include "clang/Basic/LangOptions.h"
@@ -130,6 +131,11 @@ Sema::getTemplateInstantiationArgs(NamedDecl *D,
         assert(Function->getPrimaryTemplate() && "No function template?");
         if (Function->getPrimaryTemplate()->isMemberSpecialization())
           break;
+
+        // If this function is a generic lambda specialization, we are done.
+        if (isGenericLambdaCallOperatorSpecialization(Function))
+          break;
+
       } else if (FunctionTemplateDecl *FunTmpl
                                    = Function->getDescribedFunctionTemplate()) {
         // Add the "injected" template arguments.
@@ -911,13 +917,56 @@ namespace {
     }
 
     ExprResult TransformLambdaScope(LambdaExpr *E,
-                                    CXXMethodDecl *CallOperator) {
-      CallOperator->setInstantiationOfMemberFunction(E->getCallOperator(),
-                                                     TSK_ImplicitInstantiation);
-      return TreeTransform<TemplateInstantiator>::
-         TransformLambdaScope(E, CallOperator);
+                                    CXXMethodDecl *NewCallOperator) {
+      // If a lambda is undergoing transformation for instance in the
+      // call to foo('a') below:
+      //  template<class T> void foo(T t) {
+      //    auto L1 = [](T a) { return a; };

+      //    auto L2 = [](char b) { return b; };
+      //    auto L3 = [](auto c) { return c; };
+      //  }
+      // The AST nodes of the OldCallOperators within the primary template foo
+      // are connected to the NewCallOperators within the specialization of foo.
+      //  - In the case of L1 and L2 we set the NewCallOperator to be considered
+      //    an instantiation of the OldCallOperator.
+      //  - In the generic lambda case, we set the NewTemplate to be considered
+      //    an "instantiation" of the OldTemplate.
+      // See the documentation and use of get/setInstantiationOfMemberFunction
+      // and get/setInstantiatedFromMemberTemplate to appreciate the relevance
+      // of creating these links. 
+      // And so it goes on and on with nested generic lambdas.
+      CXXMethodDecl *const OldCallOperator = E->getCallOperator();
+      FunctionTemplateDecl *const NewCallOperatorTemplate = 
+          NewCallOperator->getDescribedFunctionTemplate();
+      FunctionTemplateDecl *const OldCallOperatorTemplate = 
+          OldCallOperator->getDescribedFunctionTemplate();
+
+      if (!NewCallOperatorTemplate)
+        NewCallOperator->setInstantiationOfMemberFunction(OldCallOperator,
+                                                    TSK_ImplicitInstantiation);
+      else {
+        NewCallOperatorTemplate->setInstantiatedFromMemberTemplate(
+                                                      OldCallOperatorTemplate);
+        // Set this as a specialization so we don't go digging into the 
+        // OldCallOperatorTemplate when retrieving the 
+        // 'FunctionDecl::getTemplateInstantiationPattern()' 
+        NewCallOperatorTemplate->setMemberSpecialization();
+      }
+      return inherited::TransformLambdaScope(E, NewCallOperator);
+    }
+    TemplateParameterList *TransformTemplateParameterList(

+                              TemplateParameterList *OrigTPL)  {
+      TemplateParameterList *NewTPL = 0;
+      if (OrigTPL) {
+        if (!OrigTPL->size()) return OrigTPL; // size 0, do nothing
+         
+        DeclContext *Owner = OrigTPL->getParam(0)->getDeclContext();
+        TemplateDeclInstantiator  DeclInstantiator(getSema(), 
+                          /* DeclContext *Owner */ Owner, TemplateArgs);
+        NewTPL = DeclInstantiator.SubstTemplateParams(OrigTPL);
+      }
+      return NewTPL;  
     }
-
   private:
     ExprResult transformNonTypeTemplateParmRef(NonTypeTemplateParmDecl *parm,
                                                SourceLocation loc,
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 35f3616db6..359fb73166 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4171,6 +4171,30 @@ DeclContext *Sema::FindInstantiatedContext(SourceLocation Loc, DeclContext* DC,
 NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
                           const MultiLevelTemplateArgumentList &TemplateArgs) {
   DeclContext *ParentDC = D->getDeclContext();
+
+  // If we have a parameter from a non-dependent context with a non-dependent
+  // type it obviously can not be mapped to a different instantiated decl.
+  // Consider the code below, with explicit return types, when N gets
+  // specialized ...:
+  // template<class T> void fooT(T t) {
+  //   auto L = [](auto a) -> void { 
+  //     auto M = [](char b) -> void {
+  //       auto N = [](auto c) -> void {
+  //         int x = sizeof(a) + sizeof(b) +
+  //                 sizeof(c);
+  //       };  
+  //       N('a');
+  //     };    
+  //   };
+  //   L(3.14);
+  // }
+  // fooT('a'); 
+  // ... without this check below, findInstantiationOf fails with
+  // an assertion violation.
+  if (isa<ParmVarDecl>(D) && !ParentDC->isDependentContext() &&
+      !cast<ParmVarDecl>(D)->getType()->isInstantiationDependentType())
+    return D;
+
   if (isa<ParmVarDecl>(D) || isa<NonTypeTemplateParmDecl>(D) ||
       isa<TemplateTypeParmDecl>(D) || isa<TemplateTemplateParmDecl>(D) ||
       (ParentDC->isFunctionOrMethod() && ParentDC->isDependentContext()) ||
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index 977d0132b7..7c343635a7 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -33,6 +33,7 @@
 #include "clang/Sema/ScopeInfo.h"
 #include "clang/Sema/SemaDiagnostic.h"
 #include "clang/Sema/SemaInternal.h"
+#include "clang/Sema/Template.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <algorithm>
@@ -594,6 +595,11 @@ public:
   /// \brief Transform the captures and body of a lambda expression.
   ExprResult TransformLambdaScope(LambdaExpr *E, CXXMethodDecl *CallOperator);
 
+  TemplateParameterList *TransformTemplateParameterList(
+        TemplateParameterList *TPL) {
+    return TPL;
+  }
+
   ExprResult TransformAddressOfOperand(Expr *E);
   ExprResult TransformDependentScopeDeclRefExpr(DependentScopeDeclRefExpr *E,
                                                 bool IsAddressOfOperand);
@@ -4573,6 +4579,19 @@ template<typename Derived>
 QualType TreeTransform<Derived>::TransformDecltypeType(TypeLocBuilder &TLB,
                                                        DecltypeTypeLoc TL) {
   const DecltypeType *T = TL.getTypePtr();
+  // Don't transform a decltype construct that has already been transformed 
+  // into a non-dependent type.
+  // Allows the following to compile:
+  // auto L = [](auto a) {
+  //   return [](auto b) ->decltype(a) {
+  //     return b;
+  //  };
+  //};  
+  if (!T->isInstantiationDependentType()) {
+    DecltypeTypeLoc NewTL = TLB.push<DecltypeTypeLoc>(TL.getType());
+    NewTL.setNameLoc(TL.getNameLoc());
+    return NewTL.getType();
+  }
 
   // decltype expressions are not potentially evaluated contexts
   EnterExpressionEvaluationContext Unevaluated(SemaRef, Sema::Unevaluated, 0,
@@ -8284,24 +8303,27 @@ template<typename Derived>
 ExprResult
 TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
  
-  // FIXME: Implement nested generic lambda transformations.
-  if (E->isGenericLambda()) {
-    getSema().Diag(E->getIntroducerRange().getBegin(), 
-      diag::err_glambda_not_fully_implemented) 
-      << " template transformation of generic lambdas not implemented yet";
-    return ExprError();
-  }
-  // Transform the type of the lambda parameters and start the definition of
-  // the lambda itself.
-  TypeSourceInfo *MethodTy
-    = TransformType(E->getCallOperator()->getTypeSourceInfo());
-  if (!MethodTy)
+  getSema().PushLambdaScope();
+  LambdaScopeInfo *LSI = getSema().getCurLambda();
+  TemplateParameterList *const OrigTPL = E->getTemplateParameterList();
+  TemplateParameterList *NewTPL = 0;
+  // Transform the template parameters, and add them to the 
+  // current instantiation scope.
+  if (OrigTPL) {
+      NewTPL = getDerived().TransformTemplateParameterList(OrigTPL);
+  }
+  LSI->GLTemplateParameterList = NewTPL;
+   // Transform the type of the lambda parameters and start the definition of
+   // the lambda itself.
+  TypeSourceInfo *OldCallOpTSI = E->getCallOperator()->getTypeSourceInfo(); 
+  TypeSourceInfo *NewCallOpTSI = TransformType(OldCallOpTSI);
+  if (!NewCallOpTSI)
     return ExprError();
 
   // Create the local class that will describe the lambda.
   CXXRecordDecl *Class
     = getSema().createLambdaClosureType(E->getIntroducerRange(),
-                                        MethodTy,
+                                        NewCallOpTSI,
                                         /*KnownDependent=*/false);
   getDerived().transformedLocalDecl(E->getLambdaClass(), Class);
 
@@ -8313,19 +8335,49 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
         E->getCallOperator()->param_size(),
         0, ParamTypes, &Params))
     return ExprError();
-  getSema().PushLambdaScope();
-  LambdaScopeInfo *LSI = getSema().getCurLambda();
-  // TODO: Fix for nested lambdas
-  LSI->GLTemplateParameterList = 0;
+
   // Build the call operator.
-  CXXMethodDecl *CallOperator
+  CXXMethodDecl *NewCallOperator
     = getSema().startLambdaDefinition(Class, E->getIntroducerRange(),
-                                      MethodTy,
+                                      NewCallOpTSI,
                                       E->getCallOperator()->getLocEnd(),
                                       Params);
-  getDerived().transformAttrs(E->getCallOperator(), CallOperator);
-
-  return getDerived().TransformLambdaScope(E, CallOperator);
+  LSI->CallOperator = NewCallOperator;
+  // Fix the Decl Contexts of the parameters within the call op function 
+  // prototype.
+  getDerived().transformAttrs(E->getCallOperator(), NewCallOperator);
+  
+  TypeLoc NewCallOpTL = NewCallOpTSI->getTypeLoc();
+  FunctionProtoTypeLoc NewFPTL = NewCallOpTL.castAs<FunctionProtoTypeLoc>();
+  ParmVarDecl **NewParamDeclArray = NewFPTL.getParmArray();
+  const unsigned NewNumArgs = NewFPTL.getNumArgs();
+  for (unsigned I = 0; I < NewNumArgs; ++I) {
+      NewParamDeclArray[I]->setOwningFunction(NewCallOperator);
+  }
+  // If this is a non-generic lambda, the parameters do not get added to the
+  // current instantiation scope, so add them.  This feels kludgey.
+  // Anyway, it allows the following to compile when the enclosing template
+  // is specialized and the entire lambda expression has to be
+  // transformed.  Without this FindInstantiatedDecl causes an assertion.
+  // template<class T> void foo(T t) {
+  //    auto L = [](auto a) { 
+  //      auto M = [](char b) { <-- note: non-generic lambda
+  //        auto N = [](auto c) {
+  //          int x = sizeof(a);        
+  //          x = sizeof(b); <-- specifically this line
+  //          x = sizeof(c);
+  //        };  
+  //      };    
+  //    };
+  //  }
+  //  foo('a');
+  //
+  if (!E->isGenericLambda()) {
+    for (unsigned I = 0; I < NewNumArgs; ++I)
+      SemaRef.CurrentInstantiationScope->InstantiatedLocal(
+                                   NewParamDeclArray[I], NewParamDeclArray[I]);
+  }
+  return getDerived().TransformLambdaScope(E, NewCallOperator);
 }
 
 template<typename Derived>